TACR3 and hypogonadotropic hypogonadism: NKB, encoded by the TAC3 gene in humans and Tac2 gene in rodents, acts via the NKB receptor (NK3R; encoded by TACR3 gene in humans and Tacr3 in rodents) [78], and mutations in either TAC3 or TACR3 are associated with hypogonadotropic hypogonadism [79].